The present invention relates to an organic light emitting element, especially to an organic light emitting element of the type used in optical instruments having an optical device, such as a light source, for display, an optical circuit, an optical switch, an optical array, an optical communication element, a head for optical recording, and so forth.
A resonator structure formed by sandwiching an organic light emitting thin film between two plane reflectors is used in a conventional electro-luminescent element, as disclosed, for example, in a paper titled xe2x80x9cInvestigations on Multicolor Display by Organic Luminescent Devices with Optical Microcavity Structurexe2x80x9d, by Nakayama, Tsunoda and Nagae, The Transaction of the Institute of Electronics, Information and Communication Engineers of Japan, J77-CII, pp 437-443 (1994).
In an organic electro-luminescent element using a conventional micro-resonator structure, no means is provided for confining light proceeding in a direction parallel to the organic electro-luminescent film, and so light proceeding in that direction is lost. This problem occurs similarly in an ordinary type electro-luminescent element in which a micro-resonator structure is not used.
In the following, an explanation will be given as to why light proceeding in a direction parallel to an organic electro-luminescent film attenuates and is lost. At first, with reference to FIG. 11, a method of producing an organic light emitting element will be explained. Reference mark A indicates a substrate of the organic light emitting element, and a film B is formed by a vapor deposition method using an organic material. Regions to be masked from vapor deposition of the organic material vaporized in a vapor deposition source D are masked by a metal mask C.
In the vapor deposition apparatus shown in FIG. 11, a very narrow gap, which can be observed only by an optical microscope, exists between an edge of the mask C and the surface of the growing organic thin film. The gap is generated by unevenness of the substrate A, a bend in the mask C, a roundish shape of the edge part of the mask C, etc. Assuming that the width of the gap is 0.1 mm (=100 xcexcm), and the visual angle of the vapor deposition source D viewed from the edge part is 2 deg., the variation in the growing length of the thin film is 3.5 xcexcm (=100 xcexcmxc3x97tan (2 deg.)). That is, the thickness of the thin film changes from 100% to 0% in the interval of 3.5 xcexcm.
Usually, since the thickness of an organic thin film, such as one used for an organic light emitting element, is about 0.1 xcexcm, the ratio of the thickness of the organic thin film to the thickness changing interval is {fraction (1/35)}. Therefore, if the thin film is formed by a vapor deposition method using a mask, the angle of the edge part in the thin film is 1.6 deg. (=arctan ({fraction (1/35)})) as shown in FIG. 12. Thus, light which enters the above-mentioned edge part of the thin film is repeatedly reflected by the inner faces of the thin film as it proceeds, as shown in FIG. 12, and attenuates until finally it is extinguished.
A first object of the present invention is to provide an organic light emitting element wherein light proceeding in parallel to an organic thin film, which ordinarily would be lost, can be effectively utilized.
A second object of the present invention is to provide an organic light emitting element wherein a classical or quantum effect (correction of light emission enhancement due to the transition probability mechanism) brought about by the confinement or resonance of light is applicable.
A third object of the present invention is to provide a method of producing a highly pure organic thin film used in an organic light emitting element. To attain the above objects, the present invention has the following features.
A first feature of the present invention is to provide an organic light emitting element, including an organic thin film formed on a substrate, wherein a peripheral side surface of the organic thin film has a sectional shape such that emitted light is reflected by the side surface.
A second feature of the present invention is to provide an organic light emitting element, including an organic thin film formed on a substrate, wherein the difference between a refraction index of the organic thin film and that of an ambient substance outside the organic thin film is set such that emitted light is confined in the organic thin film by a peripheral side surface of the organic thin film.
A third feature of the present invention is to provide an organic light emitting element, including an organic thin film formed on a substrate, wherein a peripheral side surface of the organic thin film stands, in a range of 50%-90% of the thickness of the organic thin film, perpendicular to the substrate.
A fourth feature of the present invention is to provide an organic light emitting element, comprising a multilayer element formed of a translucent reflector film, a transparent electrode, a light emitting layer and a metal electrode, wherein an optical resonator is positioned between the translucent reflector film and the metal electrode on the light emitting layer in a direction perpendicular to the organic light emitting layer, and a plurality of layer parts, each of the layer parts including the light emitting layer and the metal electrode, are separately arranged in a plane parallel to the substrate, respectively, the distance between each corresponding layer in neighboring layer parts being larger than xc2xc of a wavelength of light emitted in the light emitting element.
A fifth feature of the present invention is to provide a method of producing an organic light emitting element including an organic thin film, the method comprising the steps of forming a metal thin film on the organic thin film, forming a mask of a desired pattern by physically or mechanically removing parts of the metal thin film, and applying dry etching processing to the organic thin film with the mask.
A sixth feature of the present invention is to provide an organic light emitting element having a resonator structure arranged in a direction perpendicular to a substrate of the light emitting element, the resonator structure being formed by sandwiching an organic thin film in the light emitting element between two reflectors, the organic light emitting element comprising one of a line layer structure and a dot layer structure in the organic thin film and a part of the thin films formed on the top face and bottom face of the organic thin film, in which line layers or dot layers are periodically arranged in parallel to the organic thin film, wherein each two line layers neighboring each other or each two dot layers neighboring each other have a different material composition or material structure, and the period of the arrangement, which is represented by an optical length expressed as a geometrical length x a refraction index in material of each layer, is substantially xc2xc of a wavelength of light emitted in the organic thin film.